Pelorus



Aug. 23,1927. 1,640,166

w. `o. WHITE PELORUS Filed Aug. 2s, 1924 lnvenTor. sa s2 sa Wilfrid QWhiTe 2 LLA 7/ 4 JJ bym YPatented Aug. 23, 1927. t

UNITED STATE WILFRD 0. WHITE, F NEWTON, MASSACHUSETTS.

PELORUS.

Application filed August 23, 1924. Serial No. 733,683.

rThis invention relates to ar pelorus and the object of the invention is primarily to provide an instrument suitable for aviation purposes. v

The object of the invention is further to provide a pelorus which shall be of small, light and compact form and weight so that it will take up very little space and be readily available for aviation or other purposes where a minimum of space and weight is permissible.

The ordinary type of pelorus is a comparatively large and heavy instrument. It is usually hung in a gimbal suspension with a heavy counterpoised weight enabling it to remain level on board a vessel.

The present invention provides a pelorus vmade up of thin, flat plates, disks and dials and a closely fitting hollen7 protective cover in which the leveling' feature is provided by a three-point suspension system yenabling the instrument to be leveled without the use of the usual heavy oounterpoised weight.

The invention has as its furtherobject to provide a simple, strong. accurate const-ruction, small and compact in form andof very light weight.

These and other objects and features of tl e invention will appear more fully from the accompanying description and drawings and will be particularly pointed out in the claims.

The drawings show a simple and preferred form of the invention as designed for use in aviation.

ln the drawings:

Fig. 1 is a top plan view of the device with the cover removed;

Fig. 2 is a view in central vertical section taken on the line 2-2 of Fig. 1 with the cover indicated in dotted lines;

3 is a side elevation on a small scale of the device with the cover in place.`

The base of the instrument is flat and preferably circular in shape. It is preferably formed from a light weight metal shaped and slreletonized to give it sutlic-ient rigidity with a minimum amount of weight. As shown, the base comprises an annular portion 1 presenting an external fiat circular flange 2 and an internal circular flange 8. At suitable points short legs or standards 4@ are secured to or formed. integral with the annular portion 1 and adapt the v instrument to rest upon a table or other flat support. A short vertical rib 5 is formed centrally and concentrically of the annular portion 1 and carries, preferably integral therewith, a central spider structure 6.

The spider 6 has mounted in the center thereof a vertical seat or socket 7.y This may be made of sheet metal and spun onto the spider member as shown in Fig. 2. The whole base, it will thus be seen, is compara# tively thin and is fiat and light in weight. A Vplate 8 of generally circular shape is supported at a slight distance from the base in general parallelism therewith. This plate carries the graduated dials of the pelorus and is provided with suitable means by which it may beleveled. In the preferred construction illustrated the plate has secured therein a central vertical stud. As illustrated7 this stud 9 is provided with a shank 10 passing through a central aperture in the plate and clamped thereto by a nut 11 on its lower threaded portion. The lower end of the stud 9 is of conical or convex shape as shown at 12 and seats in the upper' end of a helical compression spring 13 seated in the socket member 7. rThere is thus formed a yielding, pivotal, central support for the plate and the parts carried thereby. In order to level the plate a plurality of leveling screws are provided. As shown there are three of these leveling screws, thus providing a three-point suspension feature. Each leveling screw 14 is provided with a milled head and has its shank 15 passing through an aperture near the peripher of the plate 8 and threaded into the spi er portion of the base. Two levels 16 and 17, such as spirit-levels, are

mounted onthe plate at right angles to each 'i i" other. Thus by observing the levels and turning the leveling screws 14 the plate is readily leveled. The spring 13 which tends to separate the plate from the base acts to prevent. any lost motion and to render the operation of adjusting accurate.

An lindex line 18 on the plate indicates the fore and aft line of the aeroplane or vessel upon which the device is to be used. Upon the plate are mounted an azimuth graduated dial and a compass graduated dial in parallelism with the plate and concentricallyk and rotarily adjustable with respect to the plate and with respect to each other. For this purpose, as shown, the plate carries a plurality, here shown as three in number, of annular'.

, rabbeted, arcuate seats 19. The azimuth dial lll() lll) is shown as the outer dial and is seated in the rabbeted portion of the seats 19.' lt is graduated in the usual manner. This dial is itself rabbeted at its inner edge and forms the seat for the compass graduated dial 21 which is thus a circular disk. he stud 9 is headed at 22 so as to overlie the dial 2l and thus hold it in place, and this dial 21 in turn holds the dial 2O in place. Finger-holes 23 are provided in the dial 2O to facilitate the adjusting operation. rThis compass dial 21 is graduatec. in the usual manner.

rlhe azimuth and compass dials are clamped in adjusted position in any suitable manner. As shown, clamping screws 2st are provided threaded into the dial 20 and overlapping the edge of the dial 21. The two dials when thus Aclamped together are in turn clamped in adjusted position with res Dect to the plate by any suitable means. As shown, a shoe 25 seats against the edge of the dial 2O and is mounted to slide radially on a stud 26 mounted in a projection from the plate 8. in eccentric 27, provided with a handle 28, is mounted on the stud 2G and abuts a shoulder on the shoe'. Hence by swinging the handle 28 the dial 2O may be clamped to or nnclamped from the plate. rllhe stud 9 is provided with an axial, vertical socket to receive a shadow pin Q9. N hen not in use the shadow pins may be stored in radial apertures in the spider ot' the base and prevented trom slipping out by a light clamping spring 30.

'lhe operation of the instrument is apparent. The instrument is placed upon a table or other level support on the aeroplane or vessel with the index line 18 in or parallel with the fore and att line of the vessel. The plate is then brought to a true level by the use of the leveling screws 14. The shadow pin is inserted in its socket. An azimuth observation is taken as, for example, on the sun. The north or zero point ot' the compass dial is set in line with the 180 point of the azimuth dial, the dials are clamp-ed together, and the azimuth dial carrying therewith the compass dial is set with the proper azimuth reading at the index 18. A shadow cast by the shadow pin will then give the true course of the vessel. lt the magnetic course is desired the comp-ass dial is iirst set with respect to the azimuth dial to correspond with the proper magnetic variation.

The entire instrument is protected by a suitable cover 31 of sheet metal. This cover closely encloses the plate and dials and is provided with an annular flange. 32 at the bottom itting against the flange 2 ot the base. wt is held in place by headed studs 33 in the base which pass through key-hole slots 3a in the flange Suitable handles 35 may be provided on the cover.

rEhe entire instrument is preferably made of lightweight materials and is not only light in weight but is small and compact in form. v

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

1. ifi pelorus comprising flat base, a plate slightly spaced from and generally parallel with the base, two levels mounted on the plate at iught angles to each other, means tor adjusting the plate with respect to the base to level the plate, an azimuth graduated dial and a compass graduated dial carried by the plate in parallelism therewith and concentrically and rotarily adjustable with respect to the plate and each other, and means for clamping the dials in adjusted position.

2. A pelorus comprising a flat base, a plate slightly7 spaced from and generally parallel fith the base, a spring interposed between the plate and the base, a plurality ot leveling` screws adjustably connecting the plate and the base to permit the leveling'oi the plate, two levels mounted on 'the plate at right angles to each other, an azimuth graduated dial and a compass graduated dial carried by the plate in parallelism therewith and concentrically and rotarily adjustable with respect to the plate and each other, and means tor clamping the dials in adjusted position.

3. A pelorus comprising a fiat base, a plate slightly spaced trom andv generally parallel with the base, a compression helical spring seated centrally and vertically in the base, a vertical stud mounted centrally in the plate and having a lower conical end seated inthe sprin0m three leveling` screws passing C) through the plate and threaded into the base, two levels mounted on the plate at right angles to each other, an azimuth graduated dial and a compass graduated dial carried by the plate in parallelism therewith and concentrically and rotarily adjustable with respect to the plate and each other, and means :tor clamping tac dials in adjusted position.

ln testimony whereof7 l have signed my name to this specification.

l/VILFRID O. WVHTE.

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